Experimental investigation of permeability and Darcy-Forchheimer flow transition in metal foam with high pore density

Open -cell metal foams are a group of emerging porous materials with exceptionally large porosity that are becoming increasingly popular in a diverse range of applications such as heat exchanger and chemical reactors. However, the pressure drop characteristic of metal foam structure at high pore density remains largely unclear and unexplored. In this study, the permeabilities of 6 different copper foam samples with a pore density increasing from 35 to 130 PPI (the corresponding pore size decreases from 0.9 to 0.19 mm) were analyzed experimentally by forced convective flow test. The pressure drop characteristics were quantified by permeability and Forchheimer coefficient according to the linear Darcy equation and quadratic Forchheimer equation. The results show that increasing pore density from 35 to 95 PPI cause the permeability to drop by around 80 %, the percentage difference between Darcy and Forchheimer permeability to reduce from 50 % to 5 %, and the average pore size based critical Reynolds number to decrease from 250 to 50. However, further increasing the pore density from 95 to 130 PPI has marginal effect on these parameters. Finally, the experimental data were benchmarked with a collection of literature data and empirical models to demonstrate the distinct flow behavior in metal foam at high pore density condition. The correlation proposed by X. Yang et al. provides the most accurate prediction of copper foam permeability at high PPI with a maximum error of less than 15 %. These new findings provide important reference data to future studies on heat and mass transfer in metal foam structure for varies applications.